Hydraulic servomotor



May 15, 1962 R. F. RASMUSSEN 3,034,483

HYDRAULIC SERVOMOTOR Filed Dec. 8, 1960 4 Sheets-Sheet 1 INVENTOR. ROBERT F. RASMUSSEN ATTORNEY 1962 R. F. RASMUSSEN 3,034,483

HYDRAULIC SERVOMOTOR Filed Dec. 8, 1960 4 Sheets-Sheet 2 INVENTOR ROBERT F. RASMUSSEN BY/P FIG. 2

ATTORNEY May 15, 1962 R. F. RASMUSSEN 3,03 ,4

HYDRAULIC SERVOMOTOR Filed Dec. 8, 1960 4 Sheets-Sheet 3' CONTROL DAMPER INPUT CIRCUIT REBALANCE INVENTOR ROBERT F. RASMUSSEN an L0.

ATTORNEY y 15, 1962 R. F. RASMUSSEN 3,034,483

HYDRAULIC SERVOMOTOR Filed Dec. 8, 1960 4 Sheets-Sheet 4 REBALANCE INVENTOR ROBERT E RASMUSSEN ATTORNEY United States Patent 3,034,483 HYDRAULIC SERVOMOTOR Robert F. Rasmussen, Brooklyn Center, Minm, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Filed Dec. 8, 1960, Ser. No. 74,722 9 Claims. (Cl. 121-41) This invention relates to hydraulic servomotors of the type comprising an actuator movable under the influence of a pressure medium such as oil, and positioned by a combination of manual and automatic input signals. More specifically, the invention relates to a servomotor for an aircraft, which responds to both manual inputs and inputs from the automatic control system, or autopilot.

It has become a common practice in automatic control systems for aircraft to provide servomotors that will per mit manual control of the craft, manual control augmented by automatic damper signals from an autopilot, or complete automatic control from the autopilot, at the pilots discretion. In order to achieve this, it has been the usual practice to provide one servomotor that responds to the manual as well as damper inputs, and a separate servomotor that responds to the autopilot control signals. In such systems, the servomotor that responds to manual and damper signals conventionally provides power boost, that is, converts the pilots manual input to a higher powered hydraulically supported output.

One of the problems in these conventional systems is the fact that two servomotors must be used, rather than using a single servomotor with the attendant savings in weight, cost, and reliability. The present invention makes it possible to provide a single servomotor that combines the functions of the two servomotors conventionally used in the past, each of the functions being as fully effective in the combined single servomotor as they previously were in the individual components.

It is therefore an object of this invention to provide an improved hydraulic servomotor.

It is a further object of this invention to provide a single servomotor of the type described in which the servomotor provides mechanical outputs responsive to a combination of manual, damper, and autopilot input signals.

These and other objects of my invention will be best un derstood by reference to the following four sheets of drawings, in which:

FIGURE 1 is a perspective view of my servomotor,

FIGURE 2 is a functional schematic diagram of my servomotor when operating in the manual mode.

FIGURE 3 is a functional schematic diagram of a portion of my servomotor when operating in the damper mode, and

FIGURE 4 is a functional schematic diagram of a por tion of my servomotor when operating in the automatic control mode.

Referring now to FIGURE 1, output ram 104 is supported by cylinder 100 and coupling 106 is aifixed to the end of ram 104 by nut 105. Guide sleeve 101 is securely attached along the axis of cylinder 100 as shown and has a slot 107 located on either side thereof. Guide sleeve 101 also carries a coupling 103 as an integral part thereof. An extension 102 of output ram 104 extends from cylinder 100 into guide sleeve 101 and the end of extension 102 is pivotally attached to lever member 120 by a pin 124 extending through extension 102 and the two slots 107. Body 110 is securely attached to cylinder 100 by bolts 115 and houses the various fluid passages and hydraulic control elements that contribute to the operation of the servomotor. Electric solenoids or switching means 111 and 112 are also mounted on the back side of body 110 (not visible in FIGURE 1) and will be explained in 3,034,483 Patented May 15, 1962 greater detail below. Lever member is shaped as shown and is provided with a pin 121 for pivotally connecting link member thereto, a pin 123 for connecting link members 122 and 131 thereto, and a pin 124 for connecting extension 102 of output ram 104 thereto as above described. Link member 122 is normally connected to the manual control device (not shown) such as the pilot control stick. Link member 130 is pivotally attached to lever member 150 and lever member by pin 132. Link member 131 is coupled to shaft 134, which is arranged to be controlled by the automatic control signals during the automatic mode of operation, by coupling 133. Lever member is shaped as shown and provided with an arm 151 that is pivotally secured to body extension 114 by pin 152, and is also provided with an arm 153 that is .pivotally secured to body extension 113 by pin 154. It is apparent from this structure that any longitudinal movement of link member 130 causes movement of lever member 150 about pins 152 and 154, pins 152 and 154 being on the same axis in space.

Lever member 140 is provided with a coupling member at the upper end that permits the pivotal attachment of this member to the right end of link member 130 and the upper end of lever member 150, by means of pin 132, so that pin 132 acts as a common connecting means for these three members. Lever member 140 is also pivotally attached, by means of pin 141, to manual error input shaft or ram 142 and is also pivotally attached by pin 143 to shaft or ram 144 which is controlled by the damper signals during the damper mode of operation. The functional operation of these various lever members and link members, and the overall autopilot will be best understood by reference to the individual drawings to be de scribed below.

Power Boost or Manual Mode In FIGURE 2, the servomotor is illustrated as conditioned for manual control, with power boost, of the aircraft control surface 201. The identifying numbers of FIGURE 1 are used in FIGURE 2 for functionally corresponding components. It is, of course, apparent that FIGURE 2 is a functional and schematic representation of the servomotor and there are obvious differences in the relative lever members and link members and in their relative sizes as shown at the left of the body 110, but it is felt that there will be no confusion caused by the duplication of numbers where the function is identical to that shown in FIGURE 1.

In FIGURE 2, the airplane structure is illustrated in schematic form as element 200, to which aircraft control surface 201 is attached at one end by means of pin 202. At the other end of element 200, guide sleeve 101 is attached by means of coupling extension 103 and pin 204. Cylinder 100 supports output piston rod or ram 104 for longitudinal movement therein. It should be noted that extension 102 extends to the left of cylinder 100 as an extension of ram 104, and that it is coupled by means of pin 124 to lever member 120. Output ram 104, extension 102, pistons 240 and 250, and cooperating fluid chambers are referred to collectively as an actuator means.

As explained with reference to FIGURE 1, member 122 is normally attached to the pilots control stick and is moved in a longitudinal direction responsive to manual input commands. In order to explain the function of FIGURE 2, assume that a command has been manually initiated forcing member 122 to the right. Link member 131 (which corresponds to elements 131, 133, and 134 shown in FIGURE 1) moves freely to the right under the influence of this manual input, assuming that the automatic control system has not been engaged. Since the control surface 201 and the actuator means have 3 t not moved, as yet, pin 124 acts as a pivot point for lever member 120, and member 120 rotates in a clockwise direction, forcing link member 130 to the right, thereby forcing lever member 140 to rotate in. a colckwise direction with pin 143 acting as a pivot point for 5 member 140. This occurs because shaft or ram 144, which is not presently being used for its normal damper function, is firmly held (in the manual mode) in the position shown thereby causing point 143 to be a fixed pivot for lever member 140. Shaft or ram 142, which is pinned to lever member 140, is thereby carried to the right. Pressurized hydraulic fluid, which is resceived in line 210 and filtered by element 211, then passes through passage 212, between lands 222 and 223 of valve means or control valve means 220 through passage 243, and into chamber 245 at the left of piston 240; thereby forcing the actuator means, piston 240 and output ram 104, to the right so as to cause a clockwise rotation of surface 201 about pin 202. Fluid in chamber 246 is forced out through fluid passage 242, passage 244, between lands 221 and 222 of valve means or control valve means 220, and to the return line 213 which is connected to the sump (not shown) which forms an integral part of the hydraulic source of supply. At the same time, hydraulic pressure in line 261, which is received from an entirely separate source of hydraulic supply (not shown) passes through a filter element, into the chamber between lands 225 and 226 of the valve means or control valve means 220 into passage 254, and then into passage 251 to force the actuator means, piston 250 and output ram 104 to the right so as to cause a clockwise rotation of control surface 201 about pin 202. The fluid in chamber 255 being discharged through passage 252 and between lands 224 and 225 of valve means 220 to the return passage 262. Thus, both pistons 240 and 250 respond to the movement of valve means 220, thereby forcing the actuator means including ram 104 to the right, and causing clockwise rotation of the control surface 201.

As the actuator means moves to the right, pin 124 is also carried to the right; and assuming that the member 122 has been moved a fixed distance, lever member 120 begins to pivot about pin 123 in a counter clockwise blocked by land 234 which prevents communication between chambers 245 and 246 through passages 241, passage 237, the chamber between lands 233 and 234, passage 236 and passage 242. The fluid in the chamber to the left of land 233 is forced through passage 232, between lands 221 and 222, to the return passage 213 as bypass valve 230 is forced to the left. In the event of failure in the supply of hydraulic fluid in line 210 and passage 238, bypass valve 230 is forced to the right by spring 231 until shaft 235 engages the Wall of body 110. This opens passages 236 and 237 to the chamber between lands 233 and 234 of bypass valve 230 and permits free flow of hydraulic fluid from one side of piston 240 to the other side. By relieving the pressure across piston 240, the independent hydraulic system supplied by line 261 can continue to operate the servomotor.

Damper Mode The damper mode of operation can be seen most clearly by reference to FIGURES 2 and 3, and it should be kept in mind that the damper signals are ordinarily superimposed on manual inputs. Pin 143 acts as a fixed pivot point during normal manual operation, and shaft 142 is moved as lever member 140 is pivoted about point 143. However, for damper operation point 143- is moved in a longitudinal direction in accordance with the damper signals that are received, under the influence of output shaft or ram 144. For damper operation, points 123 and 132 act as pivot points. The inertia of the linkage including member 122 and the control stick, causes point 132 to appear stationary and movement of shaft or ram 144 and point 143 moves lever member 140 and shaft 142 to introduce the damper control signals to the valve means 220. When valve means 220 commands movement of output shaft 104 and extension 102, the movement of pin 124 causes member 120 to rotate about pivot point 123. This again results in mechanical feedback 1 to valve means 220. When manual and damper signals direction and thereby move link member 130 to the left. a

The movement of link 130 to the left causes lever memher 140 to rotate in a counter clockwise direction and pull shaft or ram 142 to the left with pin 143 still acting as a pivot point. This results in a mechanical feedback control and moves the valve means 220 to the neutral position shown in the drawing, after the control surface 201 has been moved to the required position. The control surface 201 may be restored to the neutral position shown in the drawing, if desired, by moving member 122 to the left; thereby moving shaft or ram 142 to the left, which causes the actuator means including pistons 240 and 250 to be driven to the 'left in an obvious manner. By moving member 122 back to the initial starting point, control surface 201 will rotate in a counter clockwise direction until pin 124 has reached the position shown in the drawing, at which time, valve means 220 will be moved to the neutral position by the mechanical feedback linkage and the system will be restored to the normal position as shown. It should be pointed out that whenever spool valve 220 is in its neutral position pistons 240 and 250 must be stationary.

, It should be noted that bypass valves 230 and 260 are provided, one for each of the hydraulic systems. These will be described with reference to bypass valve 230, the operation of valve 260 being identical. When hydraulic fluid is initially supplied to line 210, with valve means 220 in the neutral position as shown, it flows through passage 212 between lands 222 and 223, through passage 238 to the right face of land 234 of bypass valve 230. This forces bypass valve 230 to the left, as shown, against the force of spring 231, and compresses spring 231 until shaft 235 engages the wall of body 110. Passage 237 is then are being simultaneously used, it is apparent that they can be readily superimposed on one another by lever member and the operation of the linkage that is shown.

When a damper control signal is received, electro-hydraulic transducer 300 converts the electrical signal into movement of valve spool 310, in the usual manner. It should be noted that the electro-hydraulic transducer 300 schematically illustrated in FIGURE 3 may be any electro-mechanical flow control valve. Since the details of the transducer arenot pertinent to the understanding or explanation of the applicants invention, it is suflicient to indicate that electro-hydraulic transducer 300 is an electro-mechanical flow control valve operable to utilize electrical damper signals to direct a fluid at high (supply) pressure (which is received at line 340 and filtered by a filter 342) to passage 351 or passage 352. When transducer 300 responds to the damper signals and directs fluid at high (supply) pressure into passage 351, the flow of the fluid is blocked by lands 335 and 336 of the engage valve 330. At the same time, passage 352, which would ordinarily be the return passage, is connected through transducer 300'to passage 353; passage 353 being connected to return outlet 341. It is apparent, however, that even though electro-hydraulic transducer 300 including spool valve 310, is operated in response to the damper signals, there can be no movement of damper output shaft or ram 144 due to the condition of engage valve 330. This condition is changed by operating the switching means or solenoid valve 111, which operates in the following manner: the switching means 111 is operated by energizing coil- 344 from a suitable source of supply (not shown) which causes rod 345 and ball 346 to be driven downward so as to open passage 349 and block the upper end of passage 348. When this happens, high (supply) pressure fluid flowing through the filter 342 flows through passages 349 and 347 to the right end of engage valve 330, impinging on the right face of land 336 thereof. Engage valve 330 is thereby driven to the left, until the left end thereof engages the wall of body 110, compressing spring 331 in so doing. When the engage valve has been moved to the left, passages 351 and 376 are connected by the chamber between lands 335 and 336, and passages 352 and 375 are connected by the chamber between lands 333 and 334. Thereafter, assuming the same response of transducer 300, high (supply) pressure fluid in passage 351 flows into passage 376 and into chamber 372 to the right of piston 370, forcing piston 370 to the left and moving output shaft or ram 144 to the left. Fluid in chamber 371 then flows out through passage 375, between lands 332 and 333, through passage 352, through transducer 300, and out passage 353 to the return port 341.

Although it has just been stated that piston 37 it is moved under the influence of high pressure fluid in chamber 372, it should be noted that before such movement could have occurred, and subsequent to the movement of engage valve 330 to the left, locking mechanism 366 must be operated so as to free output shaft or ram 144 for movement. It will be understood that movement of piston 375 and ram 144 is prohibited when locking mechanism 360 is engaged as shown in FIGURE 3. To explain further, locking mechanism 360 comprises two discshaped clamping members 362 and 363 which are positioned around the periphery of a reduced diameter section of ram 144, spaced apart, and abutting shoulders 364 and 365 respectively. A spring 361 is positioned between clamping members 362 and 363 so as to hold them firmly against shoulders 364 and 365. Two annular members 373 and 374 are positioned intermediate of the clamping members 362 and 363 and the body 119. The annular members 373 and 374 are positioned around the periphery of the clamping members 362 and 363 and abut end walls 368 and 369 respectively of body 110. The annular members are in slideable engagement with body 110 so that they may be axially displaced towards one another, along the axis of ram 144. However, the force of spring 361 holding clamping means 362 and 363 against shoulders 364 and 365 also holds annular members 373 and 374 against the end walls 368 and 369 respectively, thus effectively locking, holding, or clamping ram 144 to body 168. It will be understood that the force exerted by spring 361 in holding ram 144 fixed relative to body 110 is greater than the force which may be applied to ram 144 by the fluid impinging on piston 371). When the switching means or solenoid 111 is initially operated, fluid in passage 347 also passes into passages 366 and 367, thereby impinging upon annular members 373 and 374. It will be noted that the areas upon which the fluid is impinging, upon annular members 373 and 374, is considerably larger than the area upon which the fluid is impinging upon the piston 370. Consequently, the fluid impinging upon annular members 373 and 374 exerts a suiflcient force upon spring 361 so as to compress it. When this occurs, clamping member 362 is carried away from shoulder 364 on ram 144 and clamping member 363 is carried away from shoulder 365 on ram 144, thereby freeing the ram 144 to move within the limits established by the locking mechanism 369, when it is in its unlocked position. It should be noted that this unlocking action is timed to occur just after the movement of engage valve 330, so that the fluid pressure on passage 351 is impinging on piston 370 at the instant locking mechanism 360 frees ram 144 for movement. This eliminates any backlash or slac in the servomotor. This critical timing action is controlled by designing the area of passages 366 and 367 so that the necessary delay between the operation of engage valve 330 and the operation of locking mechanism 360 is accomplished.

As ram 144 is moved, under the influence of the damper signals received in the transducer 300, potentiometer 380 provides a feedback signal that is transmitted by suitable means to the damper circuit, so as to close the servomechanism loop and null out the control signal when suitable movement of ram 144 has been realized. Wiper 382 is connected to lead 383 and moves along the resistor 381, which is secured to body 110. The ends of the potentiometer 381 are connected to leads 384 and 385. The difference of potential between leads 383 and 384 and between leads 383 and 385, and the changes thereof, indicate the movement of the output shaft or ram 144 with respect to body 110.

It should be pointed out that the arrows located at the end of supply line 340 and return line 341 are a schematic representation of a connecting means and do not represent direction of fluid flow.

Autopilot Mode It will be recalled from the description of FIGURE 1 and FIGURE 2, that output shaft or ram 134 is freely movable in body prior to the engagement of the automatic control system. This will be readily seen in FIG- URE 4, which is a functional schematic of the autopilot portion of the servomotor, and it will be noted that the various components are almost identical to those shown in FIGURE 3. For example, electro-hydraulic transducer 4% operates in the same manner as the electrohydraulic transducer 3%; switching means or solenoid 112 operates the same as described for switching means or solenoid 111; valve spool 410 operates the same as valve spool 310; and engage valve 42% operates in the same manner as engage valve 330.

However, prior to engagement of the autopilot, there is a function associated with engage valve 420, that also exists in connection with engage valve 330, but was not described in connection therewith since there was no op erative function of this arrangement in FIGURE 3. This relates to the fact that the chambers 452 and 454 on the opposite sides of piston 451 are connected by fluid passage 453, the chamber between lands 422 and 423, passage 432, passage 431, chamber 430, the bored hole 428 in engage valve 428, port 427 between lands 424 and 425, and fluid passage 455. Thus, prior to operation of engage valve 426, there is free passage of fluid across piston 451, so that the piston can be moved longitudinally, under the influence of either the manual control stick or the damper output ram 144, without interference from the hydraulic fluid that is collected in chambers 452 and 454. It will be noted in FIGURE 3 that this fluid passage also exists there, lending itself to interchangeability of parts between the damper and autopilot mechanisms, but the fluid flow does not allow movement of piston 370 to occur in FIGURE 3 due to the operation of the centering mechanism 368.

When switching means or solenoid 112 is operated, fluid in inlet passage 441 passes through filter 443, through passages 444 and 445, into chamber 446, where it impinges on the right face of land 426 and forces engage valve 424 to the left against the force of springs 421, until the end of the engage valve 420 is abutting against the body 110. Thereafter, passage 432 is blocked between lands 422 and 423, and port 427 is blocked between lands 424 and 425, thereby preventing any further fluid flow across piston 451.

Thus, after the automatic pilot has been energized, and engage valve 424) moved to the left, the fluid on either side of piston 451 (located in chambers 452 and 454) prevents movement of the piston under normal operation as a result of any outside force on output ram 134. Ram 134 is normally controlled thereafter by operation of the transducer 400. Since this ram is directly connected to link member 131 (as shown in FIG- URE 2) and that in turn to member 122, it is apparent that any movement of output ram 134 under the influence of the autopilot will be immediately felt in the manual control device (such as the pilots control stick This is the conventional parallel operation of an automatic 7 pilot servomotor. specifically with reference to FIGURE 3, it will be recalled that there is no movement of link member 131' due to operation of the damper mode, and damper control signals are therefore not felt in the control stick. This is the conventional damper mode of servomotor operation.

Referring again to FIGURE 4, there is another element shown that has not been described, and that is the overpower valve 460, which is constructed in the conventional manner. Two ball valves are shown, numbered 461 and 463, and these are held in position by springs 462 and 464, respectively. In the event that output ram 134 is in some way blocked, outside of the body 110, and there is a pressure build-up in chamber 452, for example, this excessively high pressure, when it gets to the point where it can overcome the force of spring 462, forces ball valve 461 away from the opening, and permits flow of fluid from chamber 452 to chamber 451, thereby reducing the pressure difierential across piston 451. Similarly, a high pressure in chamber 454 is relieved by ball valve 463 and spring 464, permitting flow of fluid across the valve in the opposite direction. A feedback device 470 is also shown in FIGURE 4, and the operation is identical to that shown and described in connection with FIGURE 3. Consequently, it will not be described in connection with FIGURE 4.

In view of the detailed description of the various modes of operation, it is apparent that by using the single servomotor structure shown, with the novel linkage arrangement, that all three of the normal modes of aircraft control, namely manual with power boost, damper, and autopilot, are achieved while using only a single servomotor.

What has been described is considered to be the preferred embodiment of my invention, but it is apparent that numerous modifications thereof are possible, and that the concepts involved are not necessarily limited to aircraft applications. Therefore, I do not wish to be limited to the form shown except as indicated by the following claims.

I claim:

1. A hydraulic servomotor operable in one or more of three modes of operation; the first of said modes being a manual mode including a manually operable member; the second of said modes being adamper mode including a means operable in response to damper signals; the third of said modes being an autopilot mode including means operable in response to autopilot signals; actuator means, said actuator means comprising an actuator ram and an actuator housing; valve means controlling said actuator means; linkage means connecting said manual member, said valve means, and said actuator means whereby said valve means may be operated as a resultant of the movement of said manual member and said actuator, said linkage means including a first lever member, means pivotally connecting said first lever member to said actuator housing, a second lever member, a first link member, means pivotally connecting said first lever to said second lever and said first link, means pivotally connecting said second lever to said valve means, means pivotally connecting said second lever to said means operable in response to damper signals, a second link member, means pivotally connecting said second link member to said means operable in response to autopilot signals, a third lever member, means pivotally connecting said third lever member to said first link, means pivotally connecting said third lever to said second link and to said manual member, and means pivotally connecting said third lever member to said actuator ram, said linkage means thereby permitting the adjustment of said valve means and the resulting operation of said actuator means in response to damper signals or to autopilot signals or to the movement of said manual member, said valve means further being adjustable in response to damper signals and movement of said manual member,

In connection with this, and more and said valve further being adjustable in accordance with damper signals and autopilot signals.

2. A hydraulic servomotor operatble in one or more of three modes of operation; the first of said modes being a manual mode including a manually operable member; the second of said modes being a damper mode including a means operable in response to damper signals; the third of said modes being an autopilot mode including means operable in response to autopilot signals; actuator means; valve means controlling said actuator means; and linkage means connecting said manual member, said valve means, and said actuator means whereby said valve means may be operated as a resultant of the movement of said manual member and said actuator, said linkage means including a first lever member, a second lever member, a third lever member, a first link member, and a second link member, said first lever member being pivotally connected at one end to said actuator means and at the other end to one end of said first link member, said first lever member further being pivotally connected at a point between said ends to one end of said second link member and to one end of said manual member, said second lever member having one end bifurcated, said bifurcated end being pivotally connected to said valve means housing, the other end of said second lever member being pivotally connected to the other end of said first link member and to one end of said third lever member, the other end of said third lever member being pivotally connected to said means responsive to damper signals, said third lever member being further pivotally connected to said valve means in spaced relationship to said ends, and the other end of said second link member being pivotally connected to said means responsive to autopilot signals, said linkage means thereby permitting the adjustment of said valve means and the resulting operation of said actuator means in response to damper signals or autopilot signals or to the movement of said manual member, said valve means further being adjustable in response to damper signals and movement of said manual member, and said valve further being adjustable in accordance with damper signals and autopilot signals.

3. A hydraulic servomotor comprising: a manually operable member; means operable in response to damper signals; means operable in response to autopilot signals; actuator means; valve means controlling said actuator means; and linkage means connecting said manual member, said valve means, and said actuator means whereby said valve means may be operated as a resultant of the movement of said manual member and said actuator, said linkage means including a first lever member, a second lever member, a third lever member, a first link member, and a second link member, said first lever member being pivotally connected at one point to said actuator means and at another point to said first link member, said first lever member further being pivotally connected between said points to said second link member and to said manual member; said second lever member being pivotally connected at one point to said Valve means housing'and being pivotally connected at another point to said third lever member and to said first link member, said second 7 lever being connected to said first link member at a point spaced from said connection of said first link to said first lever member, said third lever member being pivotally connected at another point to said means responsive to damper signals, said third lever member being further pivotally connected at another point to said valve means, and said second link member being pivotally connected to said means responsive to autopilot signals, said linkage means thereby permitting the adjustment of said valve means and the resulting operation of said actuator means in response to damper signals or autopilot signals or to the movement of said manual member, said valve means further being adjustable in response to damper signals and movement of said manual member, and said valve further being adjustable in accordance with damper signals and autopilot signals.

4. A hydraulic servomotor operable in one or more of three modes of operation; the first of said modes being a manual mode including a manually operable member; the second of said modes being a damper mode including means operable in response to damper signals; the third of said modes being an autopilot mode including means operable in response to autopilot signals; actuator means; control valve means controlling said actuator means; and linkage means connecting said manual member, said control valve means, and said actuator means whereby said control valve means may be operated as a resultant of the movement of said manual member and said actuator, said linkage means including a connection to said means operable in response to damper signals; said means operable in response to damper signals comprising electroshydraulic transducer means, switching means, engage valve means operable in response to said switching means, and damper output ram operable in response to signals from said electro-hydraulic transducer means, said damper output ram being normally centered and being connected to said linkage means; means operable in response to signals from said switching means to permit movement of said damper output ram, feedback means operable in response to the position of said damper output ram; said linkage means having further means connected to said means operable in response to autopilot signals, said means operable in response to autopilot signals comprising electrohydraulic transducer means, switching means, engage valve means operable in response to said switching means, and autopilot output ram operable in response to the signals from said transducer means, said autopilot output ram being normally unrestrained and being connected to said linkage means; feedback means operable in response to the movement of said autopilot output ram; and means permitting manual overpower of autopilot signals; said linkage means thereby permitting the adjustment of said Valve means and the resulting operation of said actuator means in response to damper signals or to autopilot signals or to the movement of said manual member, said valve means further being adjustable in response to damper signals and movement of said manual member, and said valve further being adjustable in accordance with damper signals and autopilot signals.

5. A hydraulic servomotor operable in one or more of three modes of operation; the first of said modes being a manual mode including a manually operable member; the second of said modes being a damper mode including means operable in response to damper signals; the third of said modes being an autopilot mode including means operable in response to autopilot signals; actuator means; control valve means controlling said actuator means; linkage means connecting said manual member, said control valve means, and said actuator means whereby said control valve means may be operated as a resultant of the movement of said manual member and said actuator, said linkage means including a connection to said means operable in response to damper signals, said means operable in response to damper signals comprising electrohydraulic transducer means, switching means, engage valve means operable in response to said switching means, and damper output ram operable in response to signals from said electro-hydraulic transducer means, said damper output ram being normally centered and being connected to said linkage means, means operable in response to signals from said switching means to permit movement of said damper output ram, feedback means operable in response to the position of said damper output ram; said linkage means having further means connected to said means operable in response to autopilot signals, and said linkage means thereby permitting the adjustment of said control valve means and the resulting operation of said actuator means in response to damper signals or autopilot signals or to the movement of said manual member, said control valve means further being adjustable in response to damper signals and movement of said manual member, and said control valve means further being adjustable in accordance with damper signals and autopilot signals.

6. A hydraulic servomotor operable in one or more of three modes of operation; the first of said modes being a manual mode including a manually operable member; the second of said modes being a damper mode including means operable in response to damper signals; the third of said modes being an autopilot mode including means operable in response to autopilot signals; actuator means; control valve means controlling said actuator means; and linkage means connecting said manual member, said control valve means and said actuator means whereby said control valve means may be operated as a resultant of the movement of said manual member and said actuator, said linkage means including a connection to said means operable in response to damper signals, and said linkage means having further means connected to said means operable in response to autopilot signals, said means operable in response to autopilot signals comprising electro-hydraulic transducer means, switching means, engage valve means operable in response to said switching means, an autopilot output ram operable in response to the signals from said transducer means, said autopilot output ram being normally unrestrained and being connected to said linkage means; feedback means operable in response to the movement of said autopilot output ram; and means permitting manual overpower of auto pilot signals; said linkage means thereby permitting the adjustment of said control valve means and the resulting operation of said actuator means in response to damper signals or autopilot signals or to the movement of said manual member, said control valve means further being adjustable in response to damper signals and movement of said manual member, and said control valve means further being adjustable in accordance with damper signals and autopilot signals.

7. A hydraulic servomotor operable in one or more of three modes of operation; the first of said modes being a manual mode including a manually operable member; the second of said modes being a damper mode including means operable in response to damper signals; the third of said modes being an autopilot mode including means operable in response to autopilot signals; dual actuator means; two independent supplies of hydraulic fluid connected to said dual actuator means; valve means controlling said supplies; and linkage means connecting said manual member, said valve means, and said dual actuator means whereby said valve means may be operated as a resultant of the movement of said manual member and said dual actuator, said linkage means including a connection to said means operable in response to damper signals, said linkage means having further means connected to said means operable in response to autopilot signals, and said linkage means thereby permitting the adjustment of said valve means and the resulting operation of said dual actuator means in response to damper signals or autopilot signals or to the movement of said manual member, and said valve means further being adjustable in response to damper signals and movement of said manual member, and said valve means still further being adjustable in accordance with damper signals and autopilot signals.

8. A servomotor operable in one or more of three modes of operation; the first of said modes being a manual mode including a manually operable member; the second of said modes being a damper mode including means operable in response to damper signals; the third of said modes being an autopilot mode including means operable in response to autopilot signals, actuator means; valve means controlling said actuator means, means connecting said manual member, said valve means, and said actuator means whereby said valve means may be operated as a resultant of the movement of said manual member and said actuator, said connecting means including a connection to said means operable in response to damper signals and to said means operable in response to autopilot signals, and said connecting means thereby permitting the adjustment of said valve means and the resulting operation of said actuator means in response to damper signals or autopilot signals or to the movement of said manual member, said valve means further being adjustable in response to damper signals and movement of said manual member, and said valve further being adjustable in accordance with damper signals and autopilot signals.

9. A hydraulic servomotor comprising a manually operable member; means operable in response to damper signals; means operable in response'to autopilot signals; actuator means; valve means'controlling said actuator means; and linkage means connecting said manual member, said valve means, and said actuator means whereby said valve means may be operated as a resultant of the movement of said manual member and said actuator means, said linkage means including a connection to said means operable in response to damper signals and to said means operable in response to autopilot signals to permit the adjustment of said valve means and the resulting operation of said actuator means in response to either (1) the damper signals, the autopilot signals, or the movement of said manual member, or (2) to a combination of the damper signals and movement of said manual memher, or (3) to the combination of the damper signals and autopilot signals.

References Cited in the file of this patent UNITED STATES PATENTS 2,678,177 Chenery et al May 11, '1954 2,877,968 Granan et al Mar. 17, 1959 2,939,653 Rasmussen et a1 June 7, 1960 2,940,694 Barlow June 14, 1960 I I OTHER REFERENCES Sedgfield et al.: German application 1,061,628, printed July 16, 1959 (KL. 62b 14/10). 

